SO(10) GUTs with gauge mediated supersymmetry breaking

We explore the phenomenology of supersymmetric SO(10) grand unified theories with gauge mediated supersymmetry breaking. We show that if SO(10) breaking proceeds through intermediate left-right symmetric gauge groups which are broken at the supersymmetry breaking scale, then perturbative unification allows the existence of only a few consistent models with very similar phenomenological consequences. We list and discuss some distinctive signatures of these theories. The most remarkable feature of the class of theories introduced here is that, unlike in models with simpler symmetry breaking chains, the allowed messenger spectrum is practically unique.Comment: 5 pages, no figures, uses REVTeX (replaced to match the version to be published in PLB: some typos corrected and a reference updated, a minor clarifying modification to the text

3d Surface Registration Using Geometric Spectrum Of Shapes

Morphometric analysis of 3D surface objects are very important in many biomedical applications and clinical diagnoses. Its critical step lies in shape comparison and registration. Considering that the deformations of most organs such as heart or brain structures are non-isometric, it is very difficult to find the correspondence between the shapes before and after deformation, and therefore, very challenging for diagnosis purposes. To solve these challenges, we propose two spectral based methods. The first method employs the variation of the eigenvalues of the Laplace-Beltrami operator of the shape and optimize a quadratic equation in order to minimize the distance between two shapes’ eigenvalues. This method can determine multi-scale, non-isometric deformations through the variation of Laplace-Beltrami spectrum of two shapes. Given two triangle meshes, the spectra can be varied from one to another with a scale function defined on each vertex. The variation is expressed as a linear interpolation of eigenvalues of the two shapes. In each iteration step, a quadratic programming problem is constructed, based on our derived spectrum variation theorem and smoothness energy constraint, to compute the spectrum variation. The derivation of the scale function is the solution of such a problem. Therefore, the final scale function can be solved by integral of the derivation from each step, which, in turn, quantitatively describes non-isometric deformations between two shapes. However, this method can not find the point to point correspondence between two shapes. Our second method, extends the first method and uses some feature points generated from the eigenvectors of two shapes to minimize the difference between two eigenvectors of the shapes in addition to their eigenvalues. In order to register two surfaces, we map both eigenvalues and eigenvectors of the Laplace-Beltrami of the shapes by optimizing an energy function. The function is defined by the integration of a smooth term to align the eigenvalues and a distance term between the eigenvectors at feature points to align the eigenvectors. The feature points are generated using the static points of certain eigenvectors of the surfaces. By using both the eigenvalues and the eigenvectors on these feature points, the computational efficiency is improved considerably without losing the accuracy in comparison to the approaches that use the eigenvectors for all vertices. The variation of the shape is expressed using a scale function defined at each vertex. Consequently, the total energy function to align the two given surfaces can be defined using the linear interpolation of the scale function derivatives. Through the optimization the energy function, the scale function can be solved and the alignment is achieved. After the alignment, the eigenvectors can be employed to calculate the point to point correspondence of the surfaces. Therefore, the proposed method can accurately define the displacement of the vertices. For both methods, we evaluate them by conducting some experiments on synthetic and real data using hippocampus and heart data. These experiments demonstrate the advantages and accuracy of our methods. We then integrate our methods to a workflow system named DataView. Using this workflow system, users can design, save, run, and share their workflow using their web-browsers without the need of installing any software and regardless of the power of their computers. We have also integrated Grid to this system therefore the same task can be executed on up to 64 different cases which will increase the performance of the system enormously

Internet Access and QoS in Ad Hoc Networks

It is likely that the increased popularity of wireless local area networks (WLANs) together with the continuous technological advances in wireless communication, also increase the interest for ad hoc networks. An ad hoc network is a wireless, autonomous, infrastructure-less network composed of stations that communicate with each other directly in a peer-to-peer fashion. When discussing mobile ad hoc networks (MANETs), we often refer to an ad hoc network where the stations cooperate in forwarding packets on behalf of each other to allow communication beyond their transmission range over multi-hop paths. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed quality of service (QoS) guarantees and multi-hop Internet access. This thesis presents conceivable solutions to both of these problems. The first two papers focus on the network layer and consider the provisioning of Internet access to ad hoc networks whereas the last two papers focus on the data link layer and investigate the provisioning of QoS to ad hoc networks. The first paper studies the interconnection between a MANET and the Internet. In addition, it evaluates three approaches for gateway discovery, which can be initiated by the gateway (proactive method), by the mobile station (reactive method) or by mixing these two approaches (hybrid method). The second paper also studies Internet access for MANETs, but with focus on micro mobility, i.e. mobile stations moving from one gateway to another. In particular, it evaluates a solution that allows mobile stations to access the Internet and roam from gateway to gateway. The third paper, gives an overview of the medium access mechanisms in IEEE 802.11 and their QoS limitations. Moreover, it proposes an enhancement to the contention-free medium access mechanism of IEEE 802.11e to provide QoS guarantees in WLANs operating in ad hoc network configuration. The fourth paper continues the work from the third paper by enhancing the scheme and dealing with the problems that occur due to hidden stations. Furthermore, it discusses how to deal with the problems that occur when moving from single-hop ad hoc networks (i.e. WLANs in ad hoc network configuration) to multi-hop ad hoc networks

Analysis of multiply antibiotic-resistant Acinetobacter baumannii belonging to Global Clone 1

Analysis of multiply antibiotic-resistant Acinetobacter baumannii belonging to Global Clone 1. A. baumannii resistant to multiple antibiotics challenges the treatment of infections caused by this organism. Multiply-antibiotic resistant isolates mainly belong to two major global clones GC1 and GC2. The objective of this study was to analyze the antibiotic resistance in Australian GC1s. Twenty six MAR GC1 isolates were recovered from Australian hospitals and examined to determine the genetic basis of their resistance. The results showed the variety of mobile elements, genomic islands, plasmids, transposons and insertion sequences that incorporate antibiotic resistance genes. AbaR islands were found to carry genes conferring resistance to multiple antibiotics. IS26-mediated deletions and homologous recombination between Tn6018 copies in the AbaR islands were shown to be responsible for generating new variants. AbaR0, the ancestor of AbaRs was found and all of the variants seen so far could be derived from it. Carbapenem resistance was rare but three strains carried the oxa23 carbapenem resistance gene in an AbaR4 island, which includes a backbone related to that of AbaR islands. In one isolate, AbaR4 was found where AbaR-type islands are usually found indicating that transposon backbone of AbaR4 can target the same position as AbaR0/AbaR3. The other two strains carried AbaR4 in a conjugative plasmid that can potentially disseminate the oxa23 gene into strains of different types. The small plasmid pRAY* was responsible for introducing the tobramycin resistance gene aadB into GC1s. Hence, this study shows the significance of plasmids incorporating additional determinants in GC1s. The most unexpected finding was horizontal transfer of DNA segments that contain ISAba1-ampC generating resistance to third generation cephalosporins. Overall, Australian GC1 isolates included a diverse collection. However, two outbreak GC1 strains were identified in a single ward of one of the Sydney hospitals. Outbreak strains persisted for a period of time and were then replaced by a GC2 strain

Supporting Internet Access and Quality of Service in Distributed Wireless Ad Hoc Networks

In this era of wireless hysteria, with continuous technological advances in wireless communication and new wireless technologies becoming standardized at a fast rate, we can expect an increased interest for wireless networks, such as ad hoc and mesh networks. These networks operate in a distributed manner, independent of any centralized device. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed QoS guarantees and multi-hop Internet access. In this thesis we present conceivable solutions to both of these problems. An autonomous, stand-alone ad hoc network is useful in many cases, such as search and rescue operations and meetings where participants wish to quickly share information. However, an ad hoc network connected to the Internet is even more desirable. This is because Internet plays an important role in the daily life of many people by offering a broad range of services. In this thesis we present AODV+, which is our solution to achieve this network interconnection between a wireless ad hoc network and the wired Internet. Providing QoS in distributed wireless networks is another challenging, but yet important, task mainly because there is no central device controlling the medium access. In this thesis we propose EDCA with Resource Reservation (EDCA/RR), which is a fully distributed MAC scheme that provides QoS guarantees by allowing applications with strict QoS requirements to reserve transmission time for contention-free medium access. Our scheme is compatible with existing standards and provides both parameterized and prioritized QoS. In addition, we present the Distributed Deterministic Channel Access (DDCA) scheme, which is a multi-hop extension of EDCA/RR and can be used in wireless mesh networks. Finally, we have complemented our simulation studies with real-world ad hoc and mesh network experiments. With the experience from these experiments, we obtained a clear insight into the limitations of wireless channels. We could conclude that a wise design of the network architecture that limits the number of consecutive wireless hops may result in a wireless mesh network that is able to satisfy users’ needs. Moreover, by using QoS mechanisms like EDCA/RR or DDCA we are able to provide different priorities to traffic flows and reserve resources for the most time-critical applications

Quantum Critical Behavior in Gauged Yukawa Matrix Field Theories with Quenched Disorder

We use the Wilson-Fisher $\epsilon$ expansion to study quantum critical behavior in gauged Yukawa matrix field theories with weak quenched disorder. We find that the resulting quantum critical behavior is in the universality class of the pure system. As in the pure system, the phase transition is typically first order, except for a limited range of parameters where it can be second order with computable critical exponents. Our results apply to the study of two-dimensional quantum antiferromagnets with weak quenched disorder and provide an example for fluctuation-induced first order phase transitions in circumstances where naively none is expected.Comment: 8 pages, LaTeX, 1 eps figur